1. Field of the Invention
This invention relates to control devices and in particular to means for controlling the alarm of a refrigeration apparatus for indicating an undesirable high temperature condition thereof.
2. Description of the Prior Art
In U.S. Pat. No. 3,158,005, of Luther J. Jungemann, which patent is owned by the assignee hereof, a temperature sensing device is shown to include a sensing bulb embedded in a block of material, such as GRS rubber compound having preselected limited thermal conductivity. In another form, the block is formed of neoprene rubber with metallic powder, such as aluminum or zinc oxide powder, dispersed therein. By controlling the conductivity of the encasing block, the temperature of the sensing bulb is maintained suitably low to prevent false operation of the control until the defrosting operation controlled thereby is completed.
Harry R. Heintzen discloses, in U.S. Pat. No. 2,208,272, a refrigerating apparatus wherein a heat conducting member, or fin, is provided for conducting heat to the sensing bulb at rates varying with the temperature of the atmosphere exteriorly of the refrigeration cabinet. The fin is connected to the main body of the evaporator, or a portion of the evaporator of low mass and of low heat storage capacity, in order that operation of the control may be effected with small heat flow from the shell. The sensing bulb is thusly caused to have a temperature between that of the inner shell of the cabinet and that of the evaporator.
In U.S. Pat. No. 2,280,202, Raymond E. Tobey shows a refrigerating apparatus having a pair of thermostats disposed on opposite sides of an insulating strip within a casing formed of a material having a high thermal conductivity. One of the thermostats is influenced primarily by the temperature of the air within the refrigerated compartment. The other of the thermostats is influenced primarily by the temperature of the air surrounding the refrigeration apparatus and by a portion of the cooling means of the refrigeration apparatus.
A defrost control for refrigerating apparatuses of Verlos G. Sharpe in U.S. Pat. No. 3,013,400, includes a sensing element contained within a chamber having a first surface exposed to the refrigerated air within the cabinet and a second surface exposed to ambient air surrounding the cabinet.
In U.S. Pat. No. 3,461,834, Howard P. Linder shows a freezer thaw alarm wherein a clip is provided for securing the sensor against an interior cabinet wall. The sensor housing is metallic.
Paul E. Summers et al show a temperature and air flow controlling apparatus in a household refrigerator, in U.S. Pat. No. 3,918,269, wherein the controlling thermostat is mounted in the above-freezing compartment on a sidewall portion thereof adjacent the cold air outlet of the evaporator.
In copending application Ser. No. 848,241 of Otfried Heybey, filed Nov. 3, 1977, which application is owned by the assignee hereof, an improved encapsulation means for providing a predetermined time delay to an embedded temperature sensing means therein is disclosed. The present invention is concerned with an improved means for mounting such an encapsulated temperature sensing means.